The concept of oxidative dehydrogenation of paraffins to olefins (ODH) has been around since at least the late 1960's. Steam cracking of paraffins was a well established technology and commercially practiced well prior to the 1960's. The perceived benefit of ODH is lower operating temperatures which in turn reduce greenhouse gas emissions. The downside to ODH processes is the potential for a decomposition (decomp). Industrial scale facilities are expensive and corporations shy away from processes which may result in a decomp. As a result ODH technology has had a difficult time gaining traction.
There are a number of United States patents assigned to Petro-Tex Chemical Corporation issued in the late 1960's that disclose the use of various ferrites in a steam cracker to produce olefins from paraffins. The patents include U.S. Pat. Nos. 3,420,911 and 3,420,912 in the names of Woskow et al. The patents teach introducing ferrites such as zinc, cadmium, and manganese ferrites (i.e. mixed oxides with iron oxide). The ferrites are introduced into a dehydrogenation zone at a temperature from about 250° C. up to about 750° C. at pressures less than 100 psi (689.476 kPa) for a time less than 2 seconds, typically from 0.005 to 0.9 seconds. The reaction appears to take place in the presence of steam that may tend to shift the equilibrium in the “wrong” direction. Additionally the reaction does not take place in the presence of a catalyst.
GB 1,213,181, which seems to correspond in part to the above Petro-Tex patents, discloses that nickel ferrite may be used in the oxidative dehydrogenation process. The reaction conditions are comparable to those of above noted Petro-Tex patents.
U.S. Pat. No. 6,891,075 issued May 10, 2005 to Liu, assigned to Symyx Technologies, Inc. teaches a catalyst for the oxidative dehydrogenation of a paraffin (alkane) such as ethane. The gaseous feedstock comprises at least the alkane and oxygen, but may also include diluents (such as argon, nitrogen, etc.) or other components (such as water or carbon dioxide). The dehydrogenation catalyst comprises at least about 2 weight % of NiO and a broad range of other elements preferably Nb, Ta, and Co. While NiO is present in the catalyst it does not appear to be the source of the oxygen for the oxidative dehydrogenation of the alkane (ethane).
U.S. Pat. No. 6,521,808 issued Feb. 18, 2003 to Ozkan et al., assigned to the Ohio State University teaches sol-gel supported catalysts for the oxidative dehydrogenation of ethane to ethylene. The catalyst appears to be a mixed metal system such as Ni—Co—Mo, V—Nb—Mo possibly doped with small amounts of Li, Na, K, Rb, and Cs on a mixed silica oxide/titanium oxide support. Again the catalyst does not provide the oxygen for the oxidative dehydrogenation, rather gaseous oxygen is included in the feed.
U.S. Pat. No. 4,450,313, issued May 22, 1984 to Eastman et al., assigned to Phillips Petroleum Company discloses a catalyst of the composition Li2O—TiO2, which is characterized by a low ethane conversion not exceeding 10%, in spite of a rather high selectivity to ethylene (92%). The major drawback of this catalyst is the high temperature of the process of oxidative dehydrogenation, which is close to or higher than 650° C.
The preparation of a supported catalyst usable for low temperature oxy-dehydrogenation of ethane to ethylene is disclosed in the U.S. Pat. No. 4,596,787 A, issued Jun. 24, 1986 assigned to Union Carbide Corp. A supported catalyst for the low temperature gas phase oxydehydrogenation of ethane to ethylene is prepared by (a) preparing a precursor solution having soluble and insoluble portions of metal compounds; (b) separating the soluble portion; (c) impregnating a catalyst support with the soluble portion; and (d) activating the impregnated support to obtain the catalyst. The calcined catalyst has the composition MoaVbNbcSbdXe. X is nothing or Li, Sc, Na, Be, Mg, Ca, Sr, Ba, Ti, Zr, Hf, Y, Ta, Cr, Fe, Co, Ni, Ce, La, Zn, Cd, Hg, Al, Tl, Pb, As, Bi, Te, U, Mn and/or W; a is 0.5-0.9; b is 0.1-0.4; c is 0.001-0.2; d is 0.001-0.1; e is 0.001-0.1 when X is an element. The patent fails to teach or suggest a co-comminution of the catalyst and the support.
Another example of the low temperature oxy-dehydrogenation of ethane to ethylene using a calcined oxide catalyst containing molybdenum, vanadium, niobium and antimony is described in the U.S. Pat. No. 4,524,236 A issued Jun. 18, 1985 and U.S. Pat. No. 4,250,346 A issued Feb. 10, 1981, both assigned to Union Carbide Corp. The calcined catalyst contains MoaVbNbcSbdXe in the form of oxides. The catalyst is prepared from a solution of soluble compounds and/or complexes and/or compounds of each of the metals. The dried catalyst is calcined by heating at 220-550° C. in air or oxygen. The catalyst precursor solutions may be supported onto a support, e.g. silica, aluminum oxide, silicon carbide, zirconia, titania or mixtures of these. The selectivity to ethylene may be greater than 65% for a 50% conversion of ethane.
The U.S. Pat. No. 6,624,116, issued Sep. 23, 2003 to Bharadwaj et al. and U.S. Pat. No. 6,566,573 issued May 20, 2003 to Bharadwaj et al., both assigned to Dow Global Technologies Inc. disclose Pt—Sn—Sb—Cu—Ag monolith systems that have been tested in an autothermal regime at T>750° C., the starting gas mixture contained hydrogen (H2:O2=2:1, GHSV=180 000 h−1). The catalyst composition is different from that of the present invention and the present invention does not contemplate the use of molecular hydrogen in the feed.
U.S. Pat. No. 4,524,236 issued Jun. 18, 1985 to McCain, assigned to Union Carbide Corporation and U.S. Pat. No. 4,899,003 issued Feb. 6, 1990 to Manyik et al., assigned to Union Carbide Chemicals and Plastics Company Inc. disclose mixed metal oxide catalysts of V—Mo—Nb—Sb. At 375-400° C. the ethane conversion reached 70% with the selectivity close to 71-73%. However, these parameters were achieved only at very low gas hourly space velocities less than 900 h−1 (i.e. 720 h−1).
U.S. Pat. No. 7,319,179 issued Jan. 15, 2008 to Lopez-Nieto et al., assigned to Consejo Superior de Investigaciones Cientificas and Universidad Politecnica de Valencia, discloses Mo—V—Te—Nb—O oxide catalysts that provided an ethane conversion of 50-70% and selectivity to ethylene up to 95% (at 38% conversion) at 360-400° C. The catalysts have the empirical formula MoTehViNbjAkOx, where A is a fifth modifying element. The catalyst is a calcined mixed oxide (at least of Mo, Te, V and Nb), optionally supported on: (i) silica, alumina and/or titania, preferably silica at 20-70 wt % of the total supported catalyst; or (ii) silicon carbide. The supported catalyst is prepared by conventional methods of precipitation from solutions, drying the precipitate then calcining.
The preparation of a Mo—Te—V—Nb composition is described in WO 2005058498 A1, published Jun. 30, 2005 (corresponding to U.S. published application 2007149390A1). Preparation of the catalyst involves preparing a slurry by combining an inert ceramic carrier with at least one solution comprising ionic species of Mo, V, Te, and Nb, drying the slurry to obtain a particulate product, precalcining the dried product at 150-350° C. in an oxygen containing atmosphere and calcining the dried product at 350-750° C. under inert atmosphere. The catalyst prepared exhibits the activity and selectivity in the oxidation reaction comparable to the non-supported catalyst.
A process for preparation of ethylene from gaseous feed comprising ethane and oxygen involving contacting the feed with a mixed oxide catalyst containing vanadium, molybdenum, tantalum and tellurium in a reactor to form effluent of ethylene is disclosed in WO 2006130288 A1, published Dec. 7, 2006, assigned to Celanese Int. Corp. The catalyst has a selectivity for ethylene of 50-80% thereby allowing oxidation of ethane to produce ethylene and acetic acid with high selectivity. The catalyst has the formula Mo1V0.3Ta0.1Te0.3Oz. The catalyst is optionally supported on a support selected from porous silicon dioxide, ignited silicon dioxide, kieselguhr, silica gel, porous and nonporous aluminum oxide, titanium dioxide, zirconium dioxide, thorium dioxide, lanthanum oxide, magnesium oxide, calcium oxide, barium oxide, tin oxide, cerium dioxide, zinc oxide, boron oxide, boron nitride, boron carbide, boron phosphate, zirconium phosphate, aluminum silicate, silicon nitride, silicon carbide, and glass, carbon, carbon-fiber, activated carbon, metal-oxide or metal networks and corresponding monoliths; or is encapsulated in a material (preferably silicon dioxide (SiO2), phosphorus pentoxide (P2O5), magnesium oxide (MgO), chromium trioxide (Cr2O3), titanium oxide (TiO2), zirconium oxide (ZrO2) or alumina (Al2O3). However, the methods of preparation of the supported compositions involve the procedures of wet chemistry (solutions are impregnated into the solid support and then the materials are dried and calcined).
U.S. Pat. No. 5,202,517 issued Apr. 13, 1993 to Minet et al., assigned to Medalert Incorporated teaches a ceramic tube for use in the conventional dehydrogenation of ethane to ethylene. The “tube” is a ceramic membrane, the ethane flows inside the tube and hydrogen diffuses out of the tube to improve the reaction kinetics. The reactive ceramic is 5 microns thick on a 1.5 to 2 mm thick support.
U.S. Pat. No. 6,818,189 issued Nov. 16, 2004 to Adris et al., assigned to SABIC teaches in the passage bridging columns 9 and 10 a process in which ceramic pellets are packed around a tubular reactor and different reactants flow around the outside and inside of the tube. The patent is directed to the oxidative dehydrogenation of ethane to ethylene.
There is a significant amount of art on the separation of ethylene and ethane using silver or copper ions in their+1 oxidation state. See U.S. Pat. No. 6,518,476 at Col. 5, lines 10-15 and Col. 16 line 12-Col. 17 line 57. NOVA Chemicals has also disclosed separation of olefins from non-olefins using ionic liquids (dithiolene in CA 2,415,064 (now abandoned)). Also see U.S. Pat. No. 6,120,692 to Exxon; U.S. Pat. No. 6,518,476 issued Feb. 11, 2003 to Union Carbide at columns 16 and 17; the abstract of JP 59172428 published Sep. 29, 1984; and the abstract of JP 59172427 published Sep. 29, 1984.
U.S. Pat. No. 8,107,825 issued Sep. 13, 2011 to Kuznicki et al., assigned to the University of Alberta contains a good outline of prior art for separation of ethane from ethylene and an adsorption method using ETS-10.
U.S. Pat. No. 7,411,107 issued Aug. 12, 2008 to Lucy et al., assigned to BP Chemicals Limited discloses a process for the separation of acetic acid from an oxidative dehydrogenation process to convert ethane to ethylene and acetic acid. The process uses a reversible complex of a metal salt (e.g. Cu or Ag) to separate ethylene (Col. 8). The patent then discloses the acetic acid may be separated from the liquids by a distillation (Col. 13 lines 35 to 40).
United States Patent application 20110245571 in the name of NOVA Chemicals (International) S.A. teaches oxidative dehydrogenation of ethane in a fluidized bed in contact with a bed of regenerative oxides to provide oxygen to the reactor. In this process “free” oxygen is not directly mixed with the feedstock reducing the likelihood of “decompositions”.
U.S. Pat. No. 3,904,703 issued Sep. 9, 1975 to Lo et al., assigned to El Paso Products Company teaches a zoned or layered oxidative reactor in which following a zone for oxidative dehydrogenation there is an “oxidation zone” following a dehydrogenation zone to oxidize hydrogen to water. Following the oxidation zone there is an adsorption bed to remove water from the reactants before they enter a subsequent dehydrogenation zone. This is to reduce the impact of water on downstream dehydrogenation catalysts.
United States Patent application 2010/0256432 published Oct. 7, 2010 in the name of Arnold et al., assigned to Lummus discloses at paragraphs 86-94 methods to remove residual oxygen from the product stream. A combustible such as hydrogen or a hydrocarbon may be added to the product stream to eliminate residual oxygen. The patent refers to a catalyst but does not disclose its composition. As noted above it may then be necessary to treat the product stream to eliminate water.
United States Patent application 2004/0010174 (now abandoned) published Jan. 15, 2004 in the name of Wang et al., assigned to ConocoPhillips Company discloses using a circulating fluidized bed (CFB) reactor (similar in design to an FCC reactor) to conduct an oxidative dehydrogenation. The disclosure teaches at paragraph 40 the catalyst acts to carry oxygen into the reactor as lattice oxygen or as adsorbed oxygen. The disclosure teaches away from adding air or oxygen to the feed stream.
U.S. Pat. No. 8,519,210 issued Aug. 27, 2013 to Arnold et al., assigned to Lummus Technology Inc. teaches that the concentration of oxygen in the feed may be limited to, with a margin below, the minimum oxygen for combustion, typically by including steam or inert gases to dilute the feed to below flammability limits.
The present invention seeks to provide a one pass process to oxidatively dehydrogenate lower paraffins (alkanes, preferably n-alkanes) to produce alpha olefins.